The human skin and underlying tissue contains numerous mechanoreceptors which are sensitive to touch, pressure, stretching and temperature. These receptors are distributed over the whole area of the human body in different depths. The sensitive area is known as the "receptive field", which exists in the skin and in the tissue below the skin, in the muscles, the sensory and motor nerves, in the wall of blood vessels, and surface membrane of the bone. The types of mechanoreceptors present are Merkel's Disk, Pacinian corpuscle, Meissner corpuscle, muscle and tendon spindles, neuromuscular junction or motor points, free nerve endings, proprioceptors and pilomotor in follicles. These are found the encapsulated sensory endings, in the dermal papillae, in the fingertips, soles, palms, scalp, tendons and genital organs etc.
These receptors are, under different conditions, sensitive in a selective fashion to stimulation parameters of forces applied to them, such as the direction, the power (mostly activated by a gentle force), and the frequency. By selective (or tuned) activation, these receptors signal the perception of the stimulation to the central nervous system, causing a comfortable relaxing sensation.
Stimulation of the skin and the underlying tissue by massage is also important in the case of injury, to improve and rehabilitate damaged tissue. In many cases, the use of controlled movement of skin and tissue is needed, and therefore, the direction, force and frequency must be accurately adjustable, to have an influence on the tissue. For example, the mechanical displacement of body fluids exerts a physical influence upon distribution of material in the vascular and lymphatic structures of such tissue. In any of these structures, the application of external forces would be expected to displace their contents, gaseous, fluid or semisolid, into regions subjected to lesser pressure. As a result, the tissue returns to its natural homogeneous formation.
Known stimulation methods are based on stroking and application of pressure on the skin surface by a therapist, through finger depression and motion, or by mechanical devices. However, the therapist cannot develop the required directional movement with great accuracy, or in a constant rhythm, and it is difficult for the therapist to maintain these movements for long periods, due to fatigue, so the resulting stimulation effects are short term. Existing mechanical devices are typically inadequate.
It would therefore be desirable to provide a stimulation device for providing physical stimulation through controlled manipulation of the skin and underlying tissue.